Solid electrolytic capacitor and method of making the same

ABSTRACT

A solid electrolytic capacitor includes a capacitor element having an element body and an anode wire extending therefrom, an anode lead electrically connected to the anode wire, a cathode lead electrically connected to the element body, and a resin package integrally sealing these parts. Each of the anode lead and the cathode lead is a conductive plate. The element body is connected to the upper surface of the cathode lead. The anode wire is connected to the upper surface of the anode lead via a conductive bolster.

This application is a division of U.S. patent application Ser. No.10/116,055, filed Apr. 5, 2002 now U.S. Pat. No. 6,625,009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid electrolytic capacitor formounting on a printed wiring board and a method of making the same.

2. Description of the Related Art

FIGS. 34 and 35 illustrate an example of prior art tantalum solidelectrolytic capacitor (hereinafter simply referred to as “solidelectrolytic capacitor”). The solid electrolytic capacitor 61 includes acathode lead 62, an anode lead 63, a capacitor element C1 and a resinpackage 65 for partially sealing these elements. The capacitor elementC1 includes an element body 64 and an anode wire 66 extending from anend surface 64 a of the element body. The element body 64 is formed witha metal layer 67 for covering the outer surfaces thereof. The metallayer 67 is electrically connected to the cathode lead 62. The anodewire 66 is electrically connected to the anode lead 63. A method formaking the solid electrolytic capacitor 61 will be described. First, anelement body 64 is connected, with a conductive adhesive 68, to acathode lead 62 formed on a manufacture lead frame (not shown). Further,an anode wire 66 extending from the element body 64 is connected, bye.g. spot welding, to an anode lead 63 similarly formed on themanufacture lead frame. Thereafter, these parts are sealed by a resinpackage 65 formed of an epoxy resin for example. Subsequently, the leads62, 63 extending outward from the resin package 65 are separated fromthe manufacture lead frame. Then, each lead 62, 63 is bent to have adesired configuration.

In bending each lead 62, 63 into a desired configuration, a considerablebending stress is exerted on the resin package 65. Therefore, the solidelectrolytic capacitor 61 need be strong enough to withstand the bendingstress. Generally, damages due to the bending stress are prevented bymaking the resin package 65 relatively thick. However, an increase inthe thickness of the resin package 65 provides a large thickness at aportion other than the element body 64, which leads to an increase inthe product size.

Recently, there is an increasing need for a solid electrolytic capacitor61 of a high capacitance. Generally, to provide a solid electrolyticcapacitor of a high capacitance, the size of the capacitor elementitself need be increased. For this purpose, the size of the solidelectrolytic capacitor accommodating the element need be increased.

However, the mounting density of a printed wiring board for mounting asolid electrolytic capacitor 61 becomes higher in accordance with thesize reduction of electronic components. Therefore, a solid electrolyticcapacitor 61 also need be reduced in size. Thus, it is not desirable toincrease the size of the solid electrolytic capacitor to provide ahigher capacitance.

Further, in the capacitor element C1, the anode wire 66 extending fromthe element body 64 is made of tantalum for example. Therefore, goodconduction cannot be established between the anode wire 66 and the anodeLead 63 made of e.g. copper because of the affinity between thematerials.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a solidelectrolytic capacitor which is capable eliminating or at least reducingthe problems described above.

According to a first aspect of the present invention, there is provideda solid electrolytic capacitor comprising a capacitor element includingan element body and a conductive wire extending therefrom, a firstelectrode electrically connected to the element body, a second electrodeelectrically connected to the conductive wire, and a resin packageintegrally sealing said parts. Each of the first electrode and thesecond electrode comprises a conductive plate and has a lower surfaceexposed at a lower surface of the resin package for serving as aterminal surface. The first electrode has an upper surface to which theelement body is connected, and the second electrode has an upper surfaceto which the conductive wire is connected via a conductive bolster.

Preferably, the lower surface of the first electrode is stepped, and theupper surface is larger in area than the terminal surface.

Preferably, the lower surface of the first electrode is partially etchedto be stepped.

Preferably, the upper surface of the second electrode has an edge formedwith a stepped portion.

Preferably, the stepped portion is formed by partially etching the uppersurface of the second electrode.

Preferably, the conductive bolster is in the form of a rectangularparallelepiped, and at least one end surface of the conductive bolsteris exposed at a side surface of the resin package.

Preferably, the conductive wire is formed of tantalum, whereas theconductive bolster is formed of nickel or an alloy containing nickel.The two members are connected to each other by resistance welding.

Preferably, the element body is connected to the upper surface of thefirst electrode with a conductive adhesive, and the conductive bolsteris connected to the upper surface of the second electrode with aconductive adhesive.

According to a second aspect of the present invention, there is provideda method of making a solid electrolytic capacitor which comprises acapacitor element including an element body and a conductive wireextending therefrom, and a resin package for sealing the capacitorelement. The method comprises preparing a plate-like fabrication frameincluding a plurality of unit regions arranged in a matrix. Each of theunit regions includes a first electrode and a second electrode havingrespective inner ends spaced from each other by a predetermineddistance. An element body of a capacitor element is connected to anupper surface of each of the first electrodes, whereas a conductive wireextending from the element body is connected to an upper surface of acorresponding one of the second electrodes via a conductive bolster. Anintermediate article is provided by resin-sealing the fabrication frameto enclose the capacitor elements while exposing the lower surfaces ofthe first electrodes and the second electrodes. The intermediate articleis divided into each of the unit regions.

Preferably, the conductive bolster is connected to the conductive wireby resistance welding. The element body is connected to the uppersurface of the first electrode with a conductive adhesive, whereas theconductive bolster is connected to the upper surface of the secondelectrode with a conductive adhesive.

According to a third aspect of the present invention, there is provideda solid electrolytic capacitor comprising a substrate having an uppersurface formed with a first and a second electrodes and a lower surfaceformed with terminal surfaces electrically connected to the first andthe second electrodes, respectively, a capacitor element including anelement body and a conductive wire extending therefrom, and a resinpackage for sealing the capacitor element. The element body is connectedto the first electrode of the substrate, and the conductive wire isconnected to the second electrode of the substrate via a conductivebolster.

Preferably, the conductive bolster is in the form of a rectangularparallelepiped, and at least one end surface of the conductive bolsteris exposed at a side surface of the resin package.

Preferably, the conductive wire is formed of tantalum, and theconductive bolster is formed of nickel or an alloy containing nickel.The two members may be connected to each other by resistance welding.

Preferably, the element body is connected to the upper surface of thefirst electrode with a conductive adhesive, whereas the conductivebolster is connected to the upper surface of the second electrode with aconductive adhesive.

According to a fourth aspect of the present invention, there is provideda method of making a solid electrolytic capacitor which comprises acapacitor element including an element body and a conductive wireextending therefrom, and a resin package for sealing the capacitorelement. The method comprises preparing a material board including aplurality of unit regions arranged in a matrix. Each of the unit regionsincludes an upper surface formed with a first and a second electrodeshaving respective inner ends spaced from each other by a predetermineddistance, and a reverse surface formed with terminal surfaceselectrically connected to the first and the second electrodes,respectively. An element body of a capacitor element is connected toeach of the first electrodes. A conductive wire extending from theelement body is connected to a corresponding one of the secondelectrodes via a conductive bolster. An intermediate article is providedby resin-sealing the material board to enclose the capacitor elementswhile exposing the terminal surfaces. The intermediate article isdivided into each of the unit regions.

Preferably, the conductive bolster is connected to the second electrodeby resistance welding. The element body is connected to the firstelectrode with a conductive adhesive, whereas the conductive bolster isconnected to the second electrode with a conductive adhesive.

Other features and advantages of the present invention will becomeclearer from the description of the preferred embodiment given belowwith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a first embodiment of thepresent invention;

FIG. 2 is a see-through top view showing the solid electrolyticcapacitor of FIG. 1;

FIG. 3 is a see-through side view showing the solid electrolyticcapacitor of FIG. 1;

FIG. 4 is a bottom view showing the solid electrolytic capacitor of FIG.1;

FIG. 5 is a sectional view of a capacitor element;

FIG. 6 is a perspective view showing another conductive bolster;

FIG. 7 is a perspective view showing still another conductive bolster;

FIG. 8 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 9 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 10 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 11 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 12 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 13 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 14 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 15 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 16 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 1;

FIG. 17 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a second embodiment of thepresent invention;

FIG. 18 is a see-through side view showing the solid electrolyticcapacitor of FIG. 17;

FIG. 19 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a third embodiment of thepresent invention;

FIG. 20 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a fourth embodiment of thepresent invention;

FIG. 21 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a fifth embodiment of thepresent invention;

FIG. 22 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a sixth embodiment of thepresent invention;

FIG. 23 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 22;

FIG. 24 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 22;

FIG. 25 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 22;

FIG. 26 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 22;

FIG. 27 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 22;

FIG. 28 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 22;

FIG. 29 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a seventh embodiment of thepresent invention;

FIG. 30 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 29;

FIG. 31 illustrates a process step of a method for making the solidelectrolytic capacitor of FIG. 29;

FIG. 32 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to an eighth embodiment of thepresent invention;

FIG. 33 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a ninth embodiment of thepresent invention;

FIG. 34 is a perspective view, which is partially cut away, showing aprior art solid electrolytic capacitor; and

FIG. 35 is a see-through side view showing the solid electrolyticcapacitor of FIG. 34.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin detail with reference to the accompanying drawings. Throughout thedrawings, the elements which are identical or similar are designated bythe same reference signs.

First, description will be made with reference to FIGS. 1-4. Thesefigures illustrate a tantalum solid electrolytic capacitor (hereinaftersimply referred to as “solid electrolytic capacitor”) according to afirst embodiment of the present invention.

The solid electrolytic capacitor 1 includes a cathode lead 2 and ananode lead 3 which are appropriately spaced from each other, a capacitorelement C connected to the cathode lead 2, a conductive bolster 5connected to the anode lead 3, and a resin package 6 of a thermosettingresin such as an epoxy resin for sealing these elements.

The capacitor element C has an element body 4 which is generally in theform of a rectangular parallelepiped. The element body 4 of thecapacitor element 4 has one end surface 4 a from which an anode wire 7extends outward. As shown in FIG. 3, the element body 4 is made up of aporous sintered body 4A formed by sintering metal powder such astantalum powder, the anode wire 7 having a base end embedded in theporous sintered body 4A, a surface oxide film 4B formed on the metalpowder to serve as a dielectric layer, a semiconductor layer 4C and agraphite layer 4D formed around the outer surfaces of the poroussintered body 4A, and a metal layer 8 made of e.g. silver for coveringthe outer surfaces of the graphite layer 4D. The metal layer B, whichfunctions as a cathode, is formed on the side surfaces 4 b and the otherend surface 4 c (See FIGS. 2 and 3). The element body 4 is connected tothe upper surface 2 a of the cathode lead 2 with a conductive adhesivefor example. The porous sintered body 4A may be alternatively formed ofaluminum or niobium for example.

The cathode lead 2 may comprise a conductive plate of copper forexample. The cathode lead 2 has a stepped lower surface. Thus, thecathode lead 2 has a thicker-walled portion 11 having a predeterminedthickness and a thinner-walled portion 12 which is thinner than thethicker-walled portion. The stepped lower surface of the cathode lead 2may be formed by half-etching.

The lower surface 2 c of the cathode lead 2 (See FIGS. 3 and 4) isexposed at the lower surface of the resin package 6 to serve as aterminal surface. The solid electrolytic capacitor 1 may besurface-mounted on a printed wiring board (not shown) by soldering thelower surface 2 c of the cathode lead 2 to a conductor pattern formed onthe surface of the printed wiring board.

The cathode lead 2 has a flat upper surface 2 a. The upper surface 2 aof the cathode lead 2 has an area which allows the mounting of thecapacitor element C.

The anode wire 7 may be made of e.g. tantalum, similarly to the poroussintered body. The anode wire 7 has a predetermined length extendingfrom a generally central portion of the end surface 4 a of the elementbody 4. The anode wire 7 is connected to the upper surface 3 a of theanode lead 3 via the conductive bolster 5.

The anode lead 3 may comprise a conductive plate of copper for example.Similarly to the cathode lead 2, the anode lead 3 has a stepped lowersurface. The anode lead 3 has a thicker-walled portion 13 having apredetermined thickness and a thinner-walled portion 14 which is thinnerthan the thicker-walled portion. The stepped lower surface of the anodelead 3 may be formed by half-etching.

The anode lead 3 has a flat upper surface 3 a which is generally flushwith the upper surface 2 a of the cathode lead 2. The upper surface 3 aof the anode lead 3 has an area which is smaller than that of the uppersurface 2 a of the cathode lead 2 and which allows the mounting of theconductive bolster 5. The lower surface 3 c of the anode lead 3 (SeeFIGS. 3 and 4) is exposed at the lower surface of the resin package 6 toserve as a terminal surface. Therefore, the solid electrolytic capacitor1 can be surface-mounted on a printed wiring board for example.

The conductive bolster 5 is generally in the form of a rectangularparallelepiped. The conductive bolster 5 is made of nickel or an alloycontaining nickel as typified by 42 alloy. The conductive bolster 5functions to electrically connect the anode wire 7, which extendsgenerally horizontally, to the anode lead 3. The conductive bolster 5 isconnected to the upper surface 3 a of the anode lead 3 with a conductiveadhesive.

In bonding the capacitor element C on the cathode lead 2, a spacing isformed between the anode wire 7 and the anode lead 3 in the absence ofthe conductive bolster 5, so that conduction cannot be establishedbetween the anode wire and the anode lead 3. According to the presentinvention, however, the conductive bolster 5 is provided forsubstantially raising the upper surface 3 a of the anode lead 3, so thatthe anode wire 7 can be electrically connected to the anode lead 3. Theconductive bolster 5 has a height which is generally equal to thedistance H (See FIG. 3) between the lower surface of the anode wire 7which extends substantially horizontally and the upper surface 3 a ofthe anode lead 3.

The upper surface 5 a of the conductive bolster 5 is connected to theanode wire 7 by resistance welding such as spot welding. It isconceivable to connect the conductive bolster 5 to the anode wire 7 withthe use of a conductive resin paste or by soldering. However, since theanode wire 7 is generally columnar, only a small contact area isprovided between the anode wire and the upper surface 5 a of theconductive bolster 5. Further, the use of a conductive resin pasteincreases the connection resistance, thereby deteriorating the impedancecharacteristics. Therefore, to provide a strong connection between theconductive bolster 5 and the anode wire 7, it is preferable to usetantalum as a material for forming the conductive bolster 5 and toselect resistance welding as a method for connecting the two members.

The resin package 6 is provided for covering the capacitor element C,the conductive bolster 5, the cathode lead 2 and the anode lead 3. Theresin package 6 provides the appearance of the solid electrolyticcapacitor 1. At the lower surface side of the resin package 6, the lowersurfaces 2 c, 3 c of the cathode lead 2 and the anode lead 3 are exposedto the outside. The exposed lower surfaces 2 c, 3 c are generally equalin size to each other (See FIG. 4).

In this way, according to the solid electrolytic capacitor 1, thecathode lead 2 supports the element body 4 and part of the cathode lead2 is exposed at the lower surface of the resin package 6 to serve as aterminal surface. On the other hand, the anode lead 3 is electricallyconnected to the conductive bolster 5 to support the anode wire 7 viathe conductive bolster. Part of the anode lead 3 is exposed at the lowersurface of the resin package 6 to serve as a terminal surface.Therefore, the solid electrolytic capacitor 1 can be surface-mounted forexample on a printed wiring board by utilizing the cathode lead 2 andthe anode lead 3 exposed at the lower surface of the resin package 6.

Moreover, unlike the prior art structure, the leads need not be bent,because the cathode lead 2 and the anode lead 3 of the solidelectrolytic capacitor 1 are exposed at the lower surface of the resinpackage 6. Thus, since a bending stress caused by bending the leads isnot exerted on the resin package 6, it is not necessary to increase thethickness of the resin package 6. Therefore, it is possible to make thecapacitor element C occupy the inner space of the resin package 6 asmuch as possible. For example, for a capacitor element C of a same givencapacitance, the resin package of the present invention can be madesmaller than that of a prior art structure, which leads a sizereduction. In other words, for a resin package of a same given size, acapacitor element C of a higher capacitance may be incorporated in theresin package 6 according to the present invention than according to theprior art structure.

The conductive bolster may have another configuration. For example, aconductive bolster 5A as shown in FIG. 6 may be used which has an uppersurface 5 a formed with a groove 15. The groove 15 may have an innerdiameter which is substantially equal to or slightly larger than theouter diameter of the anode wire 7. By disposing the anode wire 7 on thegroove 15, a large contact area is provided between the anode wire 7 andthe conductive bolster 5A. The two members can be connected to eachother more strongly by resistance welding.

A conductive bolster 5B as shown in FIG. 7 may be used which is formedwith a through-hole 16 extending in the thickness direction. Thethrough-hole 16 may have an inner diameter which is slightly larger thanthe outer diameter of the anode wire 7. The anode wire 7 and theconductive bolster 5B may be connected to each other strongly byperforming resistance welding with the anode wire 7 inserted in thethrough-hole 16.

Next, a method for making the solid electrolytic capacitor will bedescribed with reference to FIGS. 5 and 8-16. First, a description isgiven to a method for making the element body 4 of the capacitor elementC. As shown in FIG. 5, a porous sintered body 4A is first formed bycompacting metal powder such as tantalum powder followed by sintering.Then, a base end of an anode wire 7 is embedded in the porous sinteredbody 4A. Subsequently, a surface oxide film 4B as a dielectric layer isformed on the powder of the porous sintered body 4A. Then, asemiconductor layer 4C, a graphite layer 4D and a metal layer 8 arelaminated on the outer surfaces of the porous sintered body 4A.

As shown in FIG. 8, the distal end of each anode wire 7, which extendsfrom the element body 4, is welded to a band-like tie bar 21. Aplurality of capacitor elements C are connected to the tie bar 21 asspaced from each other at a predetermined pitch.

Then, as shown in FIG. 9, a bar-like conductive bolster 5 having apredetermined length is prepared. The conductive bolster bar 5 is sopositioned as to bridge the anode wires 7 of the plural capacitorelements C. Subsequently, the conductive bolster bar 5 is connected tothe anode wires 7 by resistance welding such as spot welding.

Then, the anode wires 7 are cut along the cutting lines L1 shown in FIG.9 and the tie bar 21 is removed (See FIG. 10). Thereafter, theconductive bolster bar 5is cut along the cutting lines L2 shown in FIG.10 to remove excess portions. As a result, a plurality of conductivebolsters 5 are prepared correspondingly to the capacitor elements C.

For making cathode leads 2 and anode leads 3, a plate-like frame 23 asshown in FIG. 11 is used which has a thickness of about 0.15 mm. Theplate-like frame 23 is subjected to punching. The plate-like frame 23 isformed, at edge portions thereof, with engaging holes 24 for fixing to anon-illustrated fixing base.

FIG. 12 is an enlarged view of the region A indicated by broken lines inFIG. 1. In the plate-like frame 23, a plurality of unit regions B (SeeFIG. 12), which finally become solid electrolytic capacitors, arearranged in plural rows and columns. In each of the unit regions B, ananode lead 3 and a cathode lead 2 are arranged with respective innerends spaced from each other by a predetermined distance. The leads 2, 3of the respective unit regions B are connected to each other viaperipheral portions of the plate-like frame 23 and connection portions28. As shown in FIG. 13, the reverse surfaces of the leads 2, 3 of thelead frame 23 are subjected to half-etching (See hatched portions D).Thus, thin-walled portions 12, 14 as shown in FIG. 3 are provided at thereverse surface side of the leads 2, 3.

Subsequently, a capacitor element C connected to a conductive bolster 5is connected to each pair of leads 2 and 3. Specifically, as shown inFIG. 14, conductive adhesive 30 is applied to the upper surfaces 2 a and3 a of the leads 2 and 3. The conductive adhesive 30 may be conductivepaste such as Ag paste. Then, an element body 4 is positioned on theupper surface 2 a of each cathode lead 2, whereas the conductive bolster5 is positioned on the upper surface 3 a of the corresponding anode lead3. Thus, the capacitor element C and the conductive bolster 5 aremounted on the leads 2, 3 for electrical connection.

Thereafter, a resin package 6 is formed by transfer molding.Specifically, as shown in FIG. 15, the plate-like frame 23 and theplurality of capacitor elements C are enclosed from above and belowbetween mold members 31, 32. Subsequently, a thermosetting resin such asan epoxy resin in a fluid state is injected into the cavity 33 forsolidification. As a result, the plate-like frame 23, the capacitorelements C and the conductive bolster 5 are integrally molded.

Then, as shown in FIG. 16 (which illustrates the reverse surface side ofthe region A of the plate-like frame 23), surface treatment by platingis performed with respect to the lower surfaces 2 b, 3 b of the leads 2,3. The lower surfaces 2 b, 3 b of the leads 2, 3 finally becometerminals exposed to the outside. Thereafter, the portions E indicatedby hatching in FIG. 16 are cut to be removed using a dicing saw having athickness of about 0.3 mm. In this way, by horizontally cutting theintermediate molded article, horizontally extending intermediatearticles are provided. Subsequently, the horizontally extendingintermediate articles are cut vertically to remove the portions Findicated by hatching in FIG. 16. As a result, solid electrolyticcapacitors 1 are provided, as shown in FIGS. 1 and 2.

In this way, according to the above-described manufacturing method, amultiplicity of solid electrolytic capacitors 1 can be formedsimultaneously by utilizing a plate-like frame 23. Therefore, themanufacturing cost can be reduced. In the above-described manufacturingmethod, the conductive bolster 5 is connected to the anode wire 7 beforeits connection to the anode lead 3. Alternatively, however, theconductive bolster 5 may be connected to the anode lead 3 before itsconnection to the anode wire 7.

FIG. 17 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a second embodiment of thepresent invention. In the illustrated solid electrolytic capacitor 1A,the anode lead 3 has an upper surface which is formed, at an endthereof, with a stepped portion 17. The stepped portion 17 may be formedby etching the anode lead 3 for example. The structures of otherportions are substantially the same as those of the first embodimentshown in FIG. 1.

In the case where the element body 4 is relatively large or the resinpackage 6 is deformed by compression during the molding of the resin,the lower edge of the end surface 4 a of the element body 4 may comeinto contact with the anode lead 3. However, the provision of thestepped portion 17 at the anode lead 3 increase the spacing between theend surface 4 a of the element body 4 and the anode lead 3 (See FIG.1B). This reduces the possibility that the element body 4 comes intocontact with the anode lead 3, thereby preventing a short-circuitbetween the two members. Therefore, it is possible to mount a relativelylarge element body 4, which enables the provision of a solidelectrolytic capacitor of a high capacitance.

FIG. 19 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a third embodiment of thepresent invention. In the illustrated solid electrolytic capacitor 1B,the conductive bolster 35 extends longitudinally until its opposite endsurfaces 35 a reach the respective side surfaces of the resin package 6.The opposite end surfaces 35 a of the conductive bolster 35 are exposedto the outside. The structures of other portions are substantially thesame as those of the first embodiment shown in FIG. 1.

In the above-described structure, the opposite end surfaces 35 a of theconductive bolster 35 are exposed at a location adjacent to the anodelead 3 which serves as the anode terminal. Such a structure of the solidelectrolytic capacitor 1B makes it possible to instantly distinguishbetween the anode lead 2 and the cathode lead 3, or between the anodeand the cathode just by viewing from the outside. This facilitates thehandling of the solid electrolytic capacitor B.

The solid electrolytic capacitor element 1B may be formed by thefollowing method. In this method, a conductive bolster 35 is not firstlyconnected to the anode wire 7 of a capacitor element C. Instead, abar-like conductive bolster 35 elongated to have a predetermined lengthis prepared. Subsequently, the conductive bolster bar 35 is connected toa plurality of anode leads 3 of the plate-like frame 23 in a bridgingmanner. Then, respective anode wires 7 of capacitor elements C arepositioned on the bar-like conductive bolster 35 for connection. Then,the plate-like frame 23 is cut after molding together with theconductive bolster bar 35. With this method, the conductive bolster bar35 is cut directly for conveniently exposing the opposite end surfaces35 a to the outside, which enhances the manufacturing efficiency.

FIG. 20 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a fourth embodiment of thepresent invention. In the illustrated solid electrolytic capacitor 1C,the cathode lead 2 and the anode lead 3 are not exposed at the oppositeend surfaces of the resin package 6. In the solid electrolytic capacitor1 shown in FIG. 1, the respective side surfaces 2 b, 3 b of the leads 2,3 are flush with the end surfaces of the resin package 6 for exposure tothe outside. By contrast, in the fourth embodiment, the leads 2, 3 arearranged on the inner side of the resin package 6. The respective sidesurfaces 2 b, 3 b of the leads 2, 3 are not exposed to the outside. Thatis, only the lower surfaces 2 c, 3 c of the leads 2, 3 are exposed atthe lower surface of the resin package 6. The structures of otherportions are substantially the same as those of the first embodimentshown in FIG. 1.

With this structure, the leads 2, 3 are provided on the inner side ofthe resin package 6. Therefore, when the solid electrolytic capacitor 1Cis mounted on e.g. a printed wiring board (not shown), it is possible toprevent a short circuit between the leads 2, 3 and another electroniccomponent mounted adjacent to the solid electrolytic capacitor 1C.

FIG. 21 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a fifth embodiment of thepresent invention. In the illustrated solid electrolytic capacitor 1D,the conductive bolster 35 extends longitudinally so that its oppositeend surfaces 35 a are exposed to the outside. The cathode lead 2 and theanode lead 3 are arranged on the inner side of the resin package 6. Onlythe lower surfaces 2 c, 3 c of the cathode lead 2 and the anode lead 3are exposed at the lower surface of the resin package 6. As shown inFIG. 21, the anode lead 3 connected to the conductive bolster 35 is maderelatively long similarly to the elongated conductive bolster 35. Theother portions are structurally similar to those of the first embodimentshown in FIG. 1. With this structure, the conductive bolster 35 can bestably mounted on the anode lead 3.

FIG. 22 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a sixth embodiment of thepresent invention. The illustrated solid electrolytic capacitor 1E isprovided with an insulating substrate 40 instead of a cathode lead 2 andan anode lead 3. In the solid electrolytic capacitor 1E, a capacitorelement C and a conductive bolster 5 are mounted on the substrate 40.

The substrate 40 may be formed of a glass-fiber-reinforced epoxy resin,polyimide resin such as BT-resin, or a ceramic material. The substrate40 has an upper surface 40 a formed with a cathode pad 41 and an anodepad 42. Further, the substrate has a lower surface 40 c provided withterminals 41A, 42A which are electrically connected to the cathode pad41 and the anode pad 42, respectively. One end surface 40 b of thesubstrate 40 is formed with a conductor portion 41B. The cathode pad 41is electrically connected to the terminal 41A of the lower surface 40 cvia the conductor portion 41B. The other end surface 40 d of thesubstrate 40 is formed with a conductor portion 42B. The anode pad 42 iselectrically connected to the terminal 42A of the lower surface 40 c viathe conductor portion 42B.

The element body 4 of the capacitor element C is connected to the uppersurface of the cathode pad 41 via a conductive adhesive. Further, theconductive bolster 5 is connected to the upper surface of the anode pad42 via a conductive adhesive.

The resin package 6 is formed on the upper surface 40 a of the substrate40 to cover the capacitor element C, the conductive bolster 5, part ofthe cathode pad 41 and part of the anode pad 42. The resin package 6 isnot formed at opposite ends of the substrate 40.

With this structure, instead of the leads 2, 3 of the first embodiment,the substrate 40 is utilized for supporting the capacitor element C andthe conductive bolster 5. Therefore, it is not necessary to perform theprocess step of bending the leads which has been necessary in making theprior art capacitor. Therefore, a bending stress is not exerted on theresin package 6. Thus, similarly to the first embodiment, it is possibleto make the capacitor element C occupy the inner space of the resinpackage 6 as much as possible. For example, for mounting a capacitorelement C of a same given capacitance, the resin package 6 can be madesmaller than that of a prior art structure. This leads to a sizereduction of the solid electrolytic capacitor 1E.

The method for making the solid electrolytic capacitor shown in FIG. 22will now be described below with reference to FIGS. 23-28. In thismanufacturing method, a flat material board 44 as shown in FIG. 23 isutilized. The material board 44 is formed with a plurality ofhorizontally extending slits 45 which are vertically spaced from eachother at a predetermined pitch. Between respective adjacent slits 45 aredefined band-like members 46. A plurality of unit regions G (See FIG.24) which finally become solid electrolytic capacitors are arranged ineach of the band-like members 46.

As shown in FIG. 24, a cathode pad 41 and an anode pad 42 are formed, byphotolithography for example, in each unit region G on the obversesurface of each band-like member 46. As shown in FIG. 25, a terminalportion 41A and a terminal portion 42A as a conductor pattern areformed, by photolithography for example, in each unit region G on thereverse surface of each band-like member 46. The band-like member 46 hasopposite end surfaces 46 a provided with conductor portions 41B, 42B(See FIG. 22) formed by electrolytic plating for example. The terminalportions 41A, 42A are electrically connected to the cathode pad 41 andthe anode pad 42 via conductor portions 41B, 42B, respectively.

Subsequently, as shown in FIG. 26, a capacitor element C is connected toeach pair of a cathode pad 41 and an anode pad 42. Specifically, asdescribed with reference to FIGS. 8-10 of the first embodiment, acapacitor element C is prepared as connected to a conductive bolster 5.Then, a conductive adhesive 30 is applied to the upper surface 41 a ofeach cathode pad 41 and the upper surface 42 a of each anode pad 42.Subsequently, an element body 4 is positioned on each cathode pad 41 towhich the conductive adhesive 30 has been applied. The anode wire 7extending from the element body 4 is positioned on the upper surface 5 aof the conductive bolster 5. The anode wire 7 is connected to theconductive bolster 5 by resistance welding.

Subsequently, a resin package 6 is formed. Specifically, as shown inFIG. 27, the capacitor elements C, the conductive bolsters 5, and theband-like members 46 are enclosed from above and below by mold members47, 48. Then, an epoxy resin in fluid state for example is injected intothe cavity 49 for solidification. Thus, the band-like members 46, thecapacitor elements C and the conductive bolsters 5 are integrally moldedto provide an intermediate article. In this case, the resin package 6 isnot formed at the terminal portions 41A, 42A on the reverse surface ofthe band-like members 46 so that the terminal portions are exposed tothe outside.

Then, the molded intermediate article is divided into a plurality ofsolid electrolytic capacitors. Specifically, the intermediate article iscut vertically to remove the regions J indicated by hatching in FIG. 28,thereby providing a plurality of solid electrolytic capacitors 1D asshown in FIG. 22. Also with this method, a multiplicity of solidelectrolytic capacitors 1E can be simultaneously formed by utilizing thematerial board 44. Therefore, the manufacturing cost can be reduced.

FIG. 29 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a seventh embodiment of thepresent invention. In the illustrated solid electrolytic capacitor 1F,the conductive bolster 51 is elongated to expose its opposite endsurfaces 55 a to the outside. The structure of other parts issubstantially the same as that of the sixth embodiment shown in FIG. 22.With this structure, it is possible to obtain the same advantages asthose of the third embodiment shown in FIG. 19.

Although the solid electrolytic capacitor 1F can be formed generally inthe same manner as the solid electrolytic capacitor 1E shown in FIGS.23-28, it may be formed as follows. A bar-like conductive bolster 55elongated to have a certain length is connected to capacitor elements C.As shown in FIG. 30, the conductive bolster bar 55 is connected to theanode pads 42 to bridge the anode pads 42. The element bodies 4 areconnected to the cathode pads 41 via conductive adhesive 30.

Thereafter, a resin package 6 is formed to cover the capacitor elementsC. Then, the intermediate article thus prepared is cut together with theconductive bolster 55 to remove the regions K indicated by hatching inFIG. 31. Each of the resulting conductive bolsters 55 has opposite endsurfaces 55 a which are exposed to the outside at the cut surfaces ofthe resin package 6.

In another manufacturing method, the conductive bolster bar 55 may beconnected to the anode pads 42 of the band-like member 46 before it isconnected to the capacitor elements C. Thereafter, the anode wire 7 ofeach capacitor element C is connected to the upper surface 55 a of theconductive bolster bar 55 by resistance welding.

In this way, the use of the bar-like conductive bolster 55 eliminatesthe need for individually connecting each conductive bolster 55 to acorresponding capacitor element C. Therefore, this method can shortenthe manufacturing time and save the manufacturing work, which leads toenhancement of the manufacturing efficiency.

FIG. 32 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to an eighth embodiment of thepresent invention. In the illustrated solid electrolytic capacitor 1G,the substrate 56 has opposite end surfaces 56 b, 56 d each of which isformed with a groove 57 at its intermediate portion. (The groove formedat the end surface 56 b is not illustrated.) The grooves 57 extend inthe thickness direction of the substrate 56. The anode pad 42 iselectrically connected to the terminal portion 42A formed on the lowersurface 56 c of the substrate 56 via the groove 57. The groove 57 has aninner surface provided with a conductive layer 58 formed by electrolessplating for example. The conductive layer 58 may be made of copper forexample. The conductive layer 58 is electrically connected to the anodepad 42 on the upper surface 56 a of the substrate 56. The conductivelayer 58 is also connected to the terminal portion 42A on the lowersurface 56 c of the substrate 56. The cathode pad 41 is electricallyconnected to the terminal portion 41A on the lower surface 56 c of thesubstrate 56 via the non-illustrated groove on the side of the endsurface 56 b.

The resin package 6 is formed entirely over the upper surface 56 a ofthe substrate 56. The structure of other portions is substantially thesame as that of the seventh embodiment (See FIG. 29). With thisstructure, it is possible to obtain the same advantages as thoseobtained by the seventh embodiment.

Instead of the grooves 57, the substrate 56 may be formed withthrough-holes (not shown) penetrating the substrate 56 in the thicknessdirection in this case, a conductive layer may be formed on the innersurfaces of the through-holes. The anode pad 42 (or the cathode pad 41)on the upper surface 56 a and the terminal portion 42A (or the terminalportion 41A) on the lower surface 56 c of the substrate 56 may beelectrically connected to each other via the conductive layer.

The grooves 57 may be formed at the same time as forming the slits 45 bypunching the material board 44 shown in FIG. 23. Alternatively, eachgroove may be made by forming a through-hole using a drill and thenremoving a half of the through-hole by punching.

FIG. 33 is a perspective view, which is partially cut away, showing asolid electrolytic capacitor according to a ninth embodiment of thepresent invention. In the illustrated solid electrolytic capacitor 1H,the conductive bolster 55 is elongated to expose its opposite endsurfaces 55 a to the outside. The structure of other parts issubstantially the same as that of the eighth embodiment shown in FIG.32. With this structure, it is possible to obtain the same advantages asthose of the eighth embodiment.

What is claimed is:
 1. A method of making a solid electrolytic capacitorwhich comprises a capacitor element including an element body and aconductive wire extending therefrom, and a resin package for sealing thecapacitor element, the method comprising the steps of: connecting anelement body of a capacitor element to an upper surface of each of thefirst electrodes and connecting a conductive wire extending from theelement body to an upper surface of a corresponding one of the secondelectrodes via a conductive bolster; providing an intermediate articleby resin-sealing the fabrication frame to enclose the capacitor elementswhile exposing the lower surfaces of the first electrodes and the seconda electrodes; and dividing the intermediate article into each of theunit regions; wherein, prior to mounting a plurality of capacitorelements onto the frame, the conductive bolster is connected commonly tothe conductive wires of the plurality of capacitor elements, theconductive bolster being subsequently cut between the conductive wires.2. The method of making a solid electrolytic capacitor according toclaim 1, wherein the conductive bolster is connected to the conductivewire by resistance welding, the element body being connected to theupper surface of the first electrode with a conductive adhesive, theconductive bolster being connected to the upper surface of the secondelectrode with a conductive adhesive.
 3. A method of making a solidelectrolytic capacitor which comprises a capacitor element including anelement body and a conductive wire extending therefrom, and a resinpackage for sealing the capacitor element, the method comprising thesteps of: preparing a material board including a plurality of unitregions arranged in a matrix, each of the unit regions having an uppersurface formed with a first and a second electrodes having respectiveinner ends spaced from each other by a predetermined distance and areverse surface formed with terminal surfaces electrically connected tothe first and the second electrodes, respectively; connecting an elementbody of a capacitor element to each of the first electrodes andconnecting a conductive wire extending from the element body to acorresponding one of the second electrodes via a conductive bolster;providing an intermediate article by resin-sealing the material board toenclose the capacitor elements while exposing the terminal surfaces; anddividing the intermediate article into each of the unit regions;wherein, prior to mounting a plurality of capacitor elements onto thematerial board, the conductive bolster is connected commonly to theconductive wires of the plurality of capacitor elements, the conductivebolster being subsequently cut between the conductive wires.
 4. Themethod of making a solid electrolytic capacitor according to claim 3,wherein the conductive bolster is connected to the conductive wire byresistance welding, the element body being connected to the firstelectrode with a conductive adhesive, the conductive bolster beingconnected to the second electrode with a conductive adhesive.
 5. Amethod of making a solid electrolytic capacitor which comprises acapacitor element including an element body and a conductive wireextending therefrom, and a resin package for sealing the capacitorelement, the method comprising the steps of: preparing a plate-likefabrication frame including a plurality of unit regions arranged in amatrix, each of the unit regions including a first and a secondelectrodes having respective inner ends spaced from each other by apredetermined distance; connecting an element body of a capacitorelement to an upper surface of each of the first electrodes andconnecting a conductive wire extending from the element body to an uppersurface of a corresponding one of the second electrodes via a conductivebolster; providing an intermediate article by resin-sealing thefabrication frame to enclose the capacitor elements while exposing thelower surfaces of the first electrodes and the second electrodes; anddividing the intermediate article into each of the unit regions; whereinthe resin package has an opposite pair of side surfaces, the conductivebolster being cut to be exposed at said side surfaces of the resinpackage.